[GHC] #12542: Unexpected failure.. (bug?)

[GHC]

#12542: Unexpected failure.. (bug?)
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        Reporter:  Iceland_jack      |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.0.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  GHC rejects       |  Unknown/Multiple
  valid program                      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by simonpj):

 Oddly all three work for me, in HEAD and the 8.0 branch, and GHC 8.0.1.
 Are you sure you've put in the right code?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12542#comment:2>
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